Neural and behavioral evidence for cortical reorganization in the adult somatosensory system after loss of sensory input (e.g., amputation) has been well documented. In contrast, evidence for reorganization in the adult visual system is far less clear: neural evidence is the subject of controversy, behavioral evidence is sparse, and studies combining neural and behavioral evidence have not previously been reported. Here, we report converging behavioral and neuroimaging evidence from a stroke patient (B.L.) in support of cortical reorganization in the adult human visual system. B.L.'s stroke spared the primary visual cortex (V1), but destroyed fibers that normally provide input to V1 from the upper left visual field (LVF). As a consequence, B.L. is blind in the upper LVF, and exhibits distorted perception in the lower LVF: stimuli appear vertically elongated, toward and into the blind upper LVF. For example, a square presented in the lower LVF is perceived as a rectangle extending upward. We hypothesized that the perceptual distortion was a consequence of cortical reorganization in V1. Extensive behavioral testing supported our hypothesis, and functional magnetic resonance imaging (fMRI) confirmed V1 reorganization. Together, the behavioral and fMRI data show that loss of input to V1 after a stroke leads to cortical reorganization in the adult human visual system, and provide the first evidence that reorganization of the adult visual system affects visual perception. These findings contribute to our understanding of the human adult brain's capacity to change and has implications for topics ranging from learning to recovery from brain damage.
Abstract This article describes a brain-damaged patient, J.E.S., whose pattern of impaired spelling suggested deficits affecting the graphemic output lexicon, the graphemic buffer, and the phoneme–grapheme conversion process. A remediation study was undertaken to test the assumptions of graphemic output lexicon and graphemic buffer impairment. The results supported the conclusion of an output lexicon deficit, but raised questions about the hypothesized buffer deficit. The study accordingly illustrates a way in which remediation procedures may be used to test interpretations of deficits, and the models upon which these interpretations are based.
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According to several theoretical perspectives, the spatial structure of an object is represented with respect to the object's most important axis—the object principal axis (e.g., Marr & Nishihara, 1978). For objects with an elongated or a symmetrical shape (e.g., a pen, a wine glass), available evidence suggests that the principal axis may correspond to the shape's axis of elongation or symmetry (e.g., Quinlan & Humphreys, 1993; Sekuler & Swimmer, 2000). For objects with more complex shapes, less is understood about how the principal axis is defined. We examined a class of real-world objects consisting of an elongated base and a protruding part—that is, objects with shapes resembling the capital letter 'L' (e.g., a hatchet with a large protruding blade; see Fig.2 of the supplementary materials). We asked whether the principal axis was better aligned with the object's main elongation axis (e.g., the hatchet's handle), or with an axis that spanned the global contour of the object (here referred to as the object 'contour axis'). The paradigm we used involved analyzing the pattern of reflection errors participants made in an orientation recall task. Participants were asked to report the orientation of an object they previously saw. In trials where a reflection error was made, we identified the object's axis of reflection (Fig.1). This experimental paradigm was built on the previous finding (e.g., Gregory & McCloskey, 2010) that when participants made an orientation reflection error, they tended to reflect the object across its internal principal axis. Our results suggested that the principal axes of the 'L'-shaped objects were better aligned with the object's axis of elongation (Fig.4) than with their contour axes. Overall, this finding sheds light on how individual parts within an object may interact to shape the representation of the object's global spatial structure. Meeting abstract presented at VSS 2017
Abstract Abstract A single-case study of an acquired dysgraphic patient is presented. On the basis of the patient's pattern of spelling errors, and especially his errors on words with geminate letters (e.g. “cross” spelled croos), it is argued that stored spelling representations are not simple linear sequences of letter tokens (e.g. C-R-O-S-S). Rather, it is proposed that the graphemic representations processed by the cognitive spelling mechanisms are multidimensional structures that encode separately letter position, letter identity, letter doubling, and consonant/vowel status.
In a recent study, Shoben, Wescourt, and Smith reported data concerning the semantic-episodic memory distinction proposed by Tulving. On the basis of these data they suggested that the representation for semantic information is different from that for episodic information. In the present article, we point out a number of logical problems with Shoben et al.'s arguments and suggest that because of these problems their results do not provide strong evidence in favor of a distinction between semantic and episodic memory systems. In addition, we present an experiment the results of which argue against the claim that the representation for semantic information is different from that for episodic information. We suggest that the available data do not provide strong support for the view that semantic and episodic memory are distinct systems.
